1. Field of the Invention
The present invention relates to a fatigue testing apparatus and a testing method using the same for applying stress to a sample and photographing the degree of fatigue of the sample to judge the quality of the sample.
2. Description of the Related Art
Fatigue tests per se there are known, for example, such as repeated fatigue tests and ozone exposure tests under stress.
There are known repeated fatigue tests, such as the De Mattia fatigue test, the stretch fatigue test and the flex-stretch fatigue test. The ozone exposure tests under stress, referred to above, there are known a static stretch exposure test and a dynamic stretch exposure test. As other fatigue tests there are heat relaxation breakdown (static stretch) test, rubber vibration insulator durability test, in liquid or oil expansion (linear expansion) test, steering wheel repeated durability test, and stress crack observation (e.g. thermal shock) test.
Out of the above fatigue tests, for example the De Mattia flex fatigue test is performed in accordance with JIS (Japanese Industrial Standard) K6301. During fatigue test such as the De Mattia flex fatigue test, the person in charge visually checks the condition of a sample and judges and records the degree of fatigue thereof at every certain time (e.g. 1 to 2 hours).
According to the above testing method, however, it is impossible to judge an exact generation time of crack, etc. Particularly, in the case of a black sample, it is difficult to find fine cracks or the like at the same time when they are generated.